Valve units have heretofore been provided which include a pilot valve for controlling movement on a poppet member operative to control flow at large volume rates. In such units, the poppet member is movable to a closed position in which a valve face thereof engages a valve seat to block flow between a pair of passages and is movable to an open position in which the valve face is spaced from the valve seat, with a flow path being provided between one of such passages and a space at one side of a piston portion of the poppet member to a closed position and with a pilot valve being operative between such space and a fluid reservoir for allowing movement of the poppet member to its open position. Such valve units have the advantage that the pilot valve requires little force for operation and may be operated by a solenoid and controlled from a remote location. At the same time, lifting of very heavy loads can be controlled. However, it has been found that such valves are subject to malfunctions especially where they are designed to control lifting of a load to a certain elevation and maintaining the load at such an elevation for an extended period of time. It is found that operations may occur in which the poppet member moves to an open position even though the pilot valve remains closed and as a result the load may be abruptly and rapidly lowered. The consequences of such an operation can be very serious, involving possible damage to expensive equipment and also in terms of the safety of persons who may be in the vicinity of the load when it is abruptly lowered.